The press and public have understandably focused in recent weeks on high-profile appointments such as the secretaries of state, defense and treasury as President Barack Obama builds his second-term team.They also should pay close attention to the search for a man or woman to serve as commissioner of the Social Security Administration -- a post central to the national welfare and, with a six-year term, an appointment that will continue into the next presidency.The Social Security Administration touches the lives and pocketbooks of nearly every American. With this cornerstone of our social compact under demographic pressure and political threat, the president's choice for a successor is vitally important.Washington is a land of partisan extremes these days, a place where compromise is an orphan and dealmakers are a rare sight. Inevitably, Social Security will again be a political football as Congress attempts to manage America's fiscal challenges.As a veteran of more than a few policy debates and political fights -- some of which didn't end the way I'd have liked -- I want to suggest what I think are key job requirements for the new commissioner:The nominee should bring substantial managerial experience. The Social Security Administration has roughly 62,000 employees. The agency processes payments of $4.5 billion to 6 million recipients every month. It needs a strong CEO capable of running a large and complex organization that does high-stakes work.The nominee should bring considerable policy expertise. For more than 20 years, actuaries have battled, often very publicly, over the viability of Social Security's funding mechanism. It would be profoundly foolish today to ignore the demographic challenges the retirement of baby boomers will pose to the system. The remedy should not be a band-aid, but structural reform for the long haul.The next commissioner, unlike some predecessors, should bring to the job a detailed historical knowledge of Social Security -- of decisions that have made the system stronger and of others that have weakened it.Diplomatic skills will be essential. The commissioner of Social Security will need to deal not only with criticism from his or her natural political opponents but also with substantial pressure from natural allies. A commissioner perceived as a zealot or out of touch with the private sector will have a hard time advancing arguments for a new structure of benefits or changes to Social Security's long-term funding.The commissioner of Social Security needs considerable fortitude. One of the most important aspects of the job is appearing before Congress (approximately four times a year, though the frequency can shift). For at least the next two years, that will mean confronting a Republican-controlled Congress whose leadership lives in fear of Tea Partiers whose rhetoric would suggest they'd like to see Social Security dismantled altogether.The next commissioner of Social Security will need the strength of will and command of facts necessary to stand toe-to-toe with well-prepared congressional foes.Finally, the next commissioner will have to be someone passionately dedicated to the principles that underlie the Social Security system and eloquent in articulating those principles.The vast majority of Americans want a fair system that offers dignity to the elderly while preserving economic opportunity for current and future workers. They deserve a commissioner who can ensure that Social Security operates properly, provide a vision for its long-term future and lead the fight to preserve it from political critics or demographic threats.Bill Bradley is a former Democratic U.S. senator from New Jersey and a managing director of Allen & Co.